FIG. 1 shows a first type of conventional pliers that is typically referred to as fixed type pliers because it includes a first body part 10 and a second body part 20 that are pivotally connected together at a fixed joint by means of a bolt or rivet. This type of pliers has the advantages of having less number of constituent elements and relatively simple structure, but the disadvantage of being inconvenient for use. For instance, when this fixed type of pliers is used to clamp an article having a large diameter, two jaws at front portions of the first and the second body part 10, 20 are widely opened to hold the article between them while a first handle 13 and a second handle 25 at rear portions of the two body parts 10, 20, respectively, are widely separated from each other at the same time. A user has to grip at the first handle 13 with one hand and the second handle 25 with the other hand to keep the pliers in a stable working position. It is desirable to improve the fixed type of pliers for the user to handle it more conveniently.
FIG. 2 shows a second type of conventional pliers having a push button A1 for adjusting a position at where a joint pivotally connecting two body parts of the pliers together is located. To use the pliers, the user has to hold down the push button A1 with one hand to enable moving of the joint with the other hand.
FIG. 3 shows a third type of conventional pliers being provided with an adjusting mechanism including a plurality of curved engaging grooves B1. The curved engaging grooves B1 provide different positions for a joint of the pliers to selectively engage therewith. However, it is known this type of pliers is usually used in a construction site, and thus requires a relatively strong structure to bear any applied force. To meet this structural requirement, the curved engaging grooves B1 must not be too closely spaced from one another and therefore could not provide highly precise adjustment of the joint in its position.
It is therefore desirable to develop a pair of pliers to improve the conventional pliers that are not quickly and precisely adjustable in their jaw openings.